// © Broadcom. All Rights Reserved.
// The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.
// SPDX-License-Identifier: Apache-2.0

package property

import (
	"context"
	"fmt"

	"github.com/vmware/govmomi/vim25/types"
)

// WaitOptions defines options for a property collector's WaitForUpdatesEx
// method.
type WaitOptions struct {
	Options          *types.WaitOptions
	PropagateMissing bool
	Truncated        bool
}

// WaitFilter provides helpers to construct a types.CreateFilter for use with property.Wait
type WaitFilter struct {
	types.CreateFilter
	WaitOptions
}

// Add a new ObjectSpec and PropertySpec to the WaitFilter
func (f *WaitFilter) Add(obj types.ManagedObjectReference, kind string, ps []string, set ...types.BaseSelectionSpec) *WaitFilter {
	spec := types.ObjectSpec{
		Obj:       obj,
		SelectSet: set,
	}

	pset := types.PropertySpec{
		Type:    kind,
		PathSet: ps,
	}

	if len(ps) == 0 {
		pset.All = types.NewBool(true)
	}

	f.Spec.ObjectSet = append(f.Spec.ObjectSet, spec)

	f.Spec.PropSet = append(f.Spec.PropSet, pset)

	return f
}

// Wait creates a new WaitFilter and calls the specified function for each ObjectUpdate via WaitForUpdates
func Wait(ctx context.Context, c *Collector, obj types.ManagedObjectReference, ps []string, f func([]types.PropertyChange) bool) error {
	filter := new(WaitFilter).Add(obj, obj.Type, ps)

	return WaitForUpdates(ctx, c, filter, func(updates []types.ObjectUpdate) bool {
		for _, update := range updates {
			if f(update.ChangeSet) {
				return true
			}
		}

		return false
	})
}

// WaitForUpdates waits for any of the specified properties of the specified
// managed object to change. It calls the specified function for every update it
// receives. If this function returns false, it continues waiting for
// subsequent updates. If this function returns true, it stops waiting and
// returns.
//
// To only receive updates for the specified managed object, the function
// creates a new property collector and calls CreateFilter. A new property
// collector is required because filters can only be added, not removed.
//
// If the Context is canceled, a call to CancelWaitForUpdates() is made and its
// error value is returned. The newly created collector is destroyed before this
// function returns (both in case of success or error).
//
// By default, ObjectUpdate.MissingSet faults are not propagated to the returned
// error, set WaitFilter.PropagateMissing=true to enable MissingSet fault
// propagation.
func WaitForUpdates(
	ctx context.Context,
	c *Collector,
	filter *WaitFilter,
	onUpdatesFn func([]types.ObjectUpdate) bool) (result error) {

	pc, err := c.Create(ctx)
	if err != nil {
		return err
	}

	// Attempt to destroy the collector using the background context, as the
	// specified context may have timed out or have been canceled.
	defer func() {
		if err := pc.Destroy(context.Background()); err != nil {
			if result == nil {
				result = err
			} else {
				result = fmt.Errorf(
					"destroy property collector failed with %s after failing to wait for updates: %w",
					err,
					result)
			}
		}
	}()

	// Create a property filter for the property collector.
	if _, err := pc.CreateFilter(ctx, filter.CreateFilter); err != nil {
		return err
	}

	return pc.WaitForUpdatesEx(ctx, &filter.WaitOptions, onUpdatesFn)
}

// WaitForUpdates waits for any of the specified properties of the specified
// managed object to change. It calls the specified function for every update it
// receives. If this function returns false, it continues waiting for
// subsequent updates. If this function returns true, it stops waiting and
// returns.
//
// If the Context is canceled, a call to CancelWaitForUpdates() is made and its
// error value is returned.
//
// By default, ObjectUpdate.MissingSet faults are not propagated to the returned
// error, set WaitFilter.PropagateMissing=true to enable MissingSet fault
// propagation.
func WaitForUpdatesEx(
	ctx context.Context,
	pc *Collector,
	filter *WaitFilter,
	onUpdatesFn func([]types.ObjectUpdate) bool) (result error) {

	// Create a property filter for the property collector.
	pf, err := pc.CreateFilter(ctx, filter.CreateFilter)
	if err != nil {
		return err
	}

	// Destroy the filter using the background context, as the specified context
	// may have timed out or have been canceled.
	defer func() {
		if err := pf.Destroy(context.Background()); err != nil {
			if result == nil {
				result = err
			} else {
				result = fmt.Errorf(
					"destroy property filter failed with %s after failing to wait for updates: %w",
					err,
					result)
			}
		}

	}()

	return pc.WaitForUpdatesEx(ctx, &filter.WaitOptions, onUpdatesFn)
}
